"Coachability"?

[DarthYoda]

What does this attribute mean for a players prospect of evolving? How does it work and what attributes also dictate a players prospect of evolving?

[DarthYoda]

Also, how does "!Happiness" work, and "Reputation"?

[Adam B]

From the Manual:

Coachability (Hidden)

How easy it is for coaches to get this player to improve. A high/low number here will have a significant effect on the player's likelihood of improving his skills.

Happiness: It's important to keep your players happy. If they become dissatisfied with their circumstances, their performance may drop, and they may even demand a trade.

More can be found here: Out of the Park Developments Online Manuals

As for Reputation - Do you mean your own/coaches or a players?

Your own/coaches can go in to how likely someone is to hire you (ie: the more experience you have, the better. If you start a game with multiple leagues and you're a rookie, the chance of you starting on an NHL team is very low. You need experience -- as do coaches and scouts!). This will increase over time.

If you mean players, then that's likely more tied into what role the player is - ie: a goal scorer, fighter, etc.